The present invention relates generally to high-speed multi-pair communication systems, for example, Gigabit Ethernet systems (also called 1000BASE-T standard). More particularly, the invention relates to systems and methods that provide for interoperability between different types of transceivers included in those communication systems.
In recent years, local area network (LAN) applications have become more and more prevalent as a means for providing local interconnect between personal computer systems, work stations and servers. Because of the breadth of its installed base, the 10BASE-T implementation of Ethernet remains the most pervasive, if not the dominant, network technology for LANs. However, as the need to exchange information becomes more and more imperative, and as the scope and size of the information being exchanged increases, higher and higher speeds (greater bandwidth) are required from network interconnect technologies. Among the high-speed LAN technologies currently available, fast Ethernet, commonly termed 100BASE-T, has emerged as one viable solution. Fast Ethernet technology provides a smooth, non-disruptive evolution from the 10 megabit per second (Mbps) performance of 10BASE-T applications to the 100 Mbps performance of 100BASE-T. The growing use of 100BASE-T interconnections between servers and desktops is creating a definite need for an even higher speed network technology at the backbone and server level.
Another suitable solution to this need has been provided by the IEEE 802.3 standard for gigabit Ethernet, also termed 1000BASE-T, as set forth in “IEEE Std. 802.3, 1998 Edition”, the disclosure of which is hereby expressly incorporated by reference. As described in the standard, a Gigabit Ethernet network is designed to provide 1 gigabit per second (Gbps) bandwidth in combination with the simplicity of an Ethernet architecture, at a lower cost than other technologies of comparable speed. Moreover, gigabit Ethernet offers a smooth, seamless upgrade path for present 10BASE-T or 100BASE-T Ethernet installations.
In order to obtain the requisite gigabit performance levels, gigabit Ethernet transceivers are interconnected by means of a multi-pair transmission channel architecture. In particular, transceivers are interconnected using four separate pairs of twisted Category-5 copper wires. Gigabit communication, in practice, involves the simultaneous, parallel transmission of information signals, with each signal conveying information at a rate of 250 megabits per second (Mb/s). Simultaneous, parallel transmission of four information signals over four twisted wire pairs poses substantial challenges to bidirectional communication transceivers, even though the data rate on any one wire pair is “only” 250 Mbps.
The IEEE 802.3 standard for gigabit Ethernet requires that the transceivers used in gigabit Ethernet operate according to certain transmission protocols. For example, a physical coding sublayer (PCS) included in the transceiver has certain transmit encoding rules that are based on the generation, at time n, of twelve bits, defined as Sxn[3:0], Syn[3:0], and Sgn[3:0]. Those bits are then used to generate a scrambler octet Scn[7:0]for decorrelating a data word during transmission, for generating idle and training symbols, and for randomizing the signs of the encoded data signals so that each symbol stream has no dc bias.
Prior to acceptance of the IEEE 802.3 standard, gigabit Ethernet components were already in existence (hereinafter referred to as “legacy components”), many of which are still in use today. Some of those legacy components do not operate in a manner consistent with the protocols set forth in the IEEE 802.3 standard.
Therefore, there exists a need for a system and method that provide for interoperability between various generations of gigabit Ethernet transceivers that employ different transmission encoding schemes. The present invention addresses this need.